Update some modes to new API provided by issue #31 of main repo

tetris/rulesets/pairs.lua

@@ -90,8 +90,6 @@ PAIRS.colourscheme = {
     [18] = "R"
 }
 
-PAIRS.pieces = 18
-
 PAIRS.block_offsets = {
     [1]={
         { {x=-2, y=0}, {x=-1, y=0}, {x=0, y=0}, {x=1, y=0}, {x=2, y=0} },

tetris/rulesets/randompieces.lua

@@ -33,8 +33,6 @@ function RandomPieces:generateBlockOffsets()
     return { { offsets, offsets, offsets, offsets } }
 end
 
-RandomPieces.pieces = 1
-
 RandomPieces.spawn_positions = {
     { x=4, y=5 }
 }